Staged via formation from both sides of chip

ABSTRACT

A method of fabricating a semiconductor assembly can include providing a semiconductor element having a front surface, a rear surface, and a plurality of conductive pads, forming at least one hole extending at least through a respective one of the conductive pads by processing applied to the respective conductive pad from above the front surface, forming an opening extending from the rear surface at least partially through a thickness of the semiconductor element, such that the at least one hole and the opening meet at a location between the front and rear surfaces, and forming at least one conductive element exposed at the rear surface for electrical connection to an external device, the at least one conductive element extending within the at least one hole and at least into the opening, the conductive element being electrically connected with the respective conductive pad.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.12/884,649 filed Sep. 17, 2010, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to packaging of microelectronic devices,especially the packaging of semiconductor devices.

Microelectronic elements generally comprise a thin slab of asemiconductor material, such as silicon or gallium arsenide, commonlycalled a die or a semiconductor chip. Semiconductor chips are commonlyprovided as individual, prepackaged units. In some unit designs, thesemiconductor chip is mounted to a substrate or chip carrier, which isin turn mounted on a circuit panel, such as a printed circuit board.

The active circuitry is fabricated in a first face of the semiconductorchip (e.g., a front surface). To facilitate electrical connection to theactive circuitry, the chip is provided with bond pads on the same face.The bond pads are typically placed in a regular array either around theedges of the die or, for many memory devices, in the die center. Thebond pads are generally made of a conductive metal, such as copper, oraluminum, around 0.5 μm thick. The bond pads could include a singlelayer or multiple layers of metal. The size of the bond pads will varywith the device type but will typically measure tens to hundreds ofmicrons on a side.

Through-silicon vias (TSVs) are used to connect the bond pads with asecond face of the semiconductor chip opposite the first face (e.g., arear surface). A conventional via includes a hole penetrating throughthe semiconductor chip and a conductive material extending through thehole from the first face to the second face. The bond pads may beelectrically connected to vias to allow communication between the bondpads and conductive elements on the second face of the semiconductorchip.

Conventional TSV holes may reduce the portion of the first face that canbe used to contain the active circuitry. Such a reduction in theavailable space on the first face that can be used for active circuitrymay increase the amount of silicon required to produce eachsemiconductor chip, thereby potentially increasing the cost of eachchip.

Conventional vias may have reliability challenges because of anon-optimal stress distribution inside of the vias and a mismatch of thecoefficient of thermal expansion (CTE) between a semiconductor chip, forexample, and the structure to which the chip is bonded. For example,when conductive vias within a semiconductor chip are insulated by arelatively thin and stiff dielectric material, significant stresses maybe present within the vias. In addition, when the semiconductor chip isbonded to conductive elements of a polymeric substrate, the electricalconnections between the chip and the higher CTE structure of thesubstrate will be under stress due to CTE mismatch.

Size is a significant consideration in any physical arrangement ofchips. The demand for more compact physical arrangements of chips hasbecome even more intense with the rapid progress of portable electronicdevices. Merely by way of example, devices commonly referred to as“smart phones” integrate the functions of a cellular telephone withpowerful data processors, memory and ancillary devices such as globalpositioning system receivers, electronic cameras, and local area networkconnections along with high-resolution displays and associated imageprocessing chips. Such devices can provide capabilities such as fullinternet connectivity, entertainment including full-resolution video,navigation, electronic banking and more, all in a pocket-size device.Complex portable devices require packing numerous chips into a smallspace. Moreover, some of the chips have many input and outputconnections, commonly referred to as “I/O's.” These I/O's must beinterconnected with the I/O's of other chips. The interconnectionsshould be short and should have low impedance to minimize signalpropagation delays. The components which form the interconnectionsshould not greatly increase the size of the assembly. Similar needsarise in other applications as, for example, in data servers such asthose used in internet search engines. For example, structures whichprovide numerous short, low-impedance interconnects between complexchips can increase the bandwidth of the search engine and reduce itspower consumption.

Despite the advances that have been made in semiconductor via formationand interconnection, further improvements can still be made.

SUMMARY OF TEE INVENTION

In accordance with an aspect of the invention, a method of fabricating asemiconductor assembly can include providing a semiconductor elementhaving a front surface, a rear surface remote from the front surface,and a plurality of conductive pads. Each pad can have a top surfaceexposed at the front surface and can have a bottom surface remote fromthe top surface. The method can also include forming at least one holeextending at least through a respective one of the conductive pads byprocessing applied to the respective conductive pad from above the frontsurface. The method can also include forming an opening extending fromthe rear surface at least partially through a thickness of thesemiconductor element, such that the at least one hole and the openingmeet at a location between the front and rear surfaces. The method canalso include forming at least one conductive element exposed at the rearsurface for electrical connection to an external device. The at leastone conductive element can extend within the at least one hole and atleast into the opening. The conductive element can be electricallyconnected with the respective conductive pad.

In a particular embodiment, the method can also include forming acontinuous dielectric layer partially overlying the respectiveconductive pad at least at a location above the respective conductivepad and overlying an interior surface of the semiconductor elementwithin the hole. In an exemplary embodiment, the step of forming the atleast one conductive element can form at least one conductiveinterconnect coupled directly or indirectly to the respective conductivepad and at least one conductive contact coupled to the respectiveconductive interconnect. The at least one conductive contact can beexposed at the rear surface. In a particular embodiment, the at leastone conductive contact can overlie the rear surface of the semiconductorelement. In one embodiment, the opening can have a first width in alateral direction along the rear surface, and at least one of theconductive contacts can have a second width in the lateral direction,the first width being greater than the second width. In a particularembodiment, the at least one contact can be aligned in a verticaldirection with a portion of the semiconductor element within theopening, the vertical direction being a direction of the thickness ofthe semiconductor element.

In an exemplary embodiment, the step of forming the at least one holecan be performed such that the at least one hole extends partiallythrough the thickness of the semiconductor element. In one embodiment,the step of forming the at least one hole can be performed such that theat least one hole extends up to one-third of the distance between thefront surface and the rear surface through the thickness of thesemiconductor element. The opening can extend through a remainder of thethickness of the semiconductor element that is not occupied by the atleast one hole. In a particular embodiment, the semiconductor elementcan include a plurality of active semiconductor devices. At least one ofthe plurality of conductive pads can be electrically connected with atleast one of the plurality of active semiconductor devices. In anexemplary embodiment, one or more of any of the holes and the openingcan be formed by directing a jet of fine abrasive particles towards thesemiconductor element.

In one embodiment, the step of forming the at least one hole can formtwo or more holes. The step of forming the opening can be performed suchthat the opening extends from the rear surface of the semiconductorelement to two or more of the holes. In a particular embodiment, thestep of forming the opening can be performed such that the opening has achannel shape having a length extending in a first direction along asurface of the semiconductor element, and a width extending a secondlateral direction transverse to said first direction, the length beinggreater than the width. In an exemplary embodiment, the processing thatcan be applied to the respective conductive pad from above the frontsurface can be chemical etching, laser drilling, or plasma etching. Inone embodiment, a method of fabricating a stacked assembly can includeat least first and second semiconductor assemblies. The method can alsoinclude the step of electrically connecting the first semiconductorassembly with the second semiconductor assembly.

In a particular embodiment, the step of forming at least one conductiveelement can form at least one conductive interconnect exposed at therear surface for electrical connection to an external device, and atleast one conductive via. The at least one conductive interconnect canextend at least into the opening. Each via can extend within arespective hole and can be coupled to a respective conductiveinterconnect and a respective pad. In one embodiment, the step offorming at least one conductive element can form two or more conductiveinterconnects. A plurality of the holes can meet the opening and theconductive interconnects can extend at least within the opening to therespective vias. In an exemplary embodiment, each conductiveinterconnect can be formed by plating a metal layer overlying at leastan inner surface of the opening. The conductive interconnect can conformto a contour of the opening. In a particular embodiment, the conductiveinterconnects can extend along respective portions of the inner surfaceof the opening.

In one embodiment, the step of forming at least one conductive elementcan be performed so as to form two or more conductive interconnects atleast within the opening. Each of the two or more conductiveinterconnects can extend to a single one of the conductive vias. In anexemplary embodiment, each conductive interconnect can define aninternal space. In a particular embodiment, the method can also includethe step of filling each internal space with a dielectric material. Inone embodiment, the method can also include the step of forming adielectric layer overlying at least the inner surface of the opening.Each conductive interconnect can fill a volume between surfaces of thedielectric layer.

In an exemplary embodiment, the method can also include forming adielectric region within the opening and forming an aperture extendingthrough the dielectric region. The aperture can have constant diameteror can taper in a direction towards the front surface and can have acontour not conforming to a contour of the opening. The step of formingthe at least one conductive element can form a respective one of theconductive interconnects at least within the aperture. In a particularembodiment, the respective one of the conductive interconnects can havea cylindrical or frusto-conical shape. In one embodiment, the respectiveone of the conductive interconnects can be formed by plating a metallayer onto an inner surface of the aperture. In an exemplary embodiment,the respective one of the conductive interconnects can define aninternal space.

In a particular embodiment, the method can also include the step offilling the internal space with a dielectric material. In oneembodiment, the respective one of the conductive interconnects can filla volume within the aperture. In an exemplary embodiment, at least oneof the conductive vias can be formed by plating a metal layer overlyingat least an inner surface of the respective one of the holes. Theconductive via can conform to a contour of the hole. In a particularembodiment, each of the at least one of the conductive vias can definean internal space. In one embodiment, the method can also include thestep of filling each internal space with a dielectric material. In anexemplary embodiment, the method can also include the step of forming adielectric layer overlying at least the inner surface of the respectiveone of the holes. Each of the at least one of the conductive vias canfill a volume between surfaces of the dielectric layer.

In one embodiment, the method can also include, prior to the step offorming the opening, forming a dielectric region within each hole andforming an aperture extending through each dielectric region. Theaperture can have constant diameter or can taper in a direction towardsthe rear surface and can have a contour not conforming to a contour ofthe hole. The step of forming the at least one conductive element canform a respective one of the conductive vias at least within theaperture. In an exemplary embodiment, the respective one of theconductive vias can have a cylindrical or frusto-conical shape. In aparticular embodiment, the respective one of the conductive vias can beformed by plating a metal layer overlying an inner surface of theaperture. In one embodiment, each of the at least one of the conductivevias can define an internal space.

In an exemplary embodiment, the method can also include the step offilling each internal space with a dielectric material. In a particularembodiment, each of the at least one of the conductive vias can fill avolume within the aperture. In one embodiment, each conductive via canhave a first width at a top end thereof, and each conductiveinterconnect can have a second width at a bottom end thereof that meetsthe top end of a respective one of the conductive vias, the second widthbeing different than the first width. In an exemplary embodiment, thestep of forming at least one conductive element can be performed so asto form at least one conductive interconnect exposed at the rear surfacefor electrical connection to an external device. The at least oneconductive interconnect can extend within the at least one hole and atleast into the opening. Each conductive interconnect can extend to arespective pad.

In a particular embodiment, the step of forming at least one conductiveelement can form two or more conductive interconnects. A plurality ofthe holes can meet the opening and the conductive interconnects canextend at least within the opening and through the respective holes tothe respective pads. In one embodiment, the method can also includeforming a dielectric region within the hole and the opening and formingan aperture extending through the dielectric region. The aperture canhave a contour not conforming to either a contour of the hole or acontour of the opening. The step of forming the at least one conductiveelement can form a respective one of the conductive interconnects atleast within the aperture. In an exemplary embodiment, the respectiveone of the conductive interconnects can have a cylindrical orfrusto-conical shape. In a particular embodiment, the respective one ofthe conductive interconnects can be formed by plating a metal layeroverlying an inner surface of the aperture.

In accordance with an aspect of the invention, a semiconductor assemblyincludes a semiconductor element having a front surface, a rear surfaceremote from the front surface, and an opening extending from the rearsurface at least partially through the thickness of the semiconductorelement. The semiconductor element can further include a plurality ofconductive pads at the front surface. The semiconductor assembly canalso include at least one hole extending through the conductive pad andpartially through the thickness of the semiconductor element. The atleast one hole can meet the opening at a location between the front andrear surfaces. At the location where the hole and the opening meet,interior surfaces of the hole and the opening can extend at differentangles relative to the rear surface such that there can be a step changebetween slopes of the interior surfaces of the hole and the opening. Thesemiconductor assembly can also include a continuous dielectric layerpartially overlying the conductive pad at least at a location above theconductive pad and overlying an interior surface of the semiconductormaterial within the hole. The semiconductor assembly can also include atleast one conductive element electrically contacting the respectiveconductive pad. The at least one conductive element can have a firstportion exposed at the rear surface for electrical connection with anexternal device. The at least one conductive element can have a secondportion overlying the continuous dielectric layer at least at a locationabove the conductive pad.

In accordance with an aspect of the invention, a semiconductor assemblyincludes a semiconductor element having a front surface, a rear surfaceremote from the front surface, and an opening extending from the rearsurface at least partially through the thickness of the semiconductorelement. The semiconductor element can further include a plurality ofconductive pads at the front surface. The semiconductor assembly canalso include at least one hole extending through the conductive pad andpartially through the thickness of the semiconductor element. The atleast one hole can meet the opening at a location between the front andrear surfaces. At the location where the hole and the opening meet,interior surfaces of the hole and the opening can extend at differentangles relative to the rear surface such that there can be a step changebetween slopes of the interior surfaces of the hole and the opening. Thesemiconductor assembly can also include a continuous dielectric layeroverlying an interior surface of the conductive pad within the hole andoverlying an interior surface of the semiconductor material within thehole. The semiconductor assembly can also include at least oneconductive element electrically contacting the respective conductivepad. The at least one conductive element can have a first portionexposed at the rear surface for electrical connection with an externaldevice. The at least one conductive element can have a second portionoverlying the continuous dielectric layer.

In a particular embodiment, the at least one conductive pad can have anoutwardly facing surface facing away from the semiconductor element. Atleast a portion of the dielectric layer can contact the outwardly-facingsurface. In one embodiment, the at least one conductive element caninclude at least one conductive interconnect coupled directly orindirectly to the respective conductive pad and at least one conductivecontact coupled to the respective conductive interconnect. The at leastone conductive contact can be exposed at the rear surface. In anexemplary embodiment, the at least one conductive contact can overliethe rear surface of the semiconductor element. In a particularembodiment, the opening can have a first width in a lateral directionalong the rear surface, and at least one of the conductive contacts canhave a second width in the lateral direction, the first width beinggreater than the second width.

In one embodiment, the at least one contact can be aligned in a verticaldirection with a portion of the semiconductor element within theopening, the vertical direction being a direction of the thickness ofthe semiconductor element. In an exemplary embodiment, the semiconductorelement can include a plurality of active semiconductor devices and atleast one of the plurality of conductive pads can be electricallyconnected with at least one of the plurality of active semiconductordevices. In a particular embodiment, the at least one hole can be two ormore holes, and the opening can extend from the rear surface of thesemiconductor element to two or more of the holes. In one embodiment,the opening can have a channel shape having a length extending in afirst direction along a surface of the semiconductor element, and awidth extending a second lateral direction transverse to said firstdirection, the length being greater than the width.

In an exemplary embodiment, the at least one conductive pad can have anoutwardly facing surface facing away from the semiconductor element. Atleast a portion of the at least one conductive element can overlie theoutwardly-facing surface and can be electrically connected thereto. In aparticular embodiment, a stacked assembly can include at least first andsecond semiconductor assemblies. The first semiconductor assembly can beelectrically connected with the second semiconductor assembly. In oneembodiment, the at least one conductive element can include at least oneconductive interconnect exposed at the rear surface for electricalconnection to an external device, and at least one conductive via. Theat least one conductive interconnect can extend at least into theopening. Each via can extend within a respective hole and can be coupledto a respective conductive interconnect and a respective pad. In anexemplary embodiment, the at least one conductive element can includetwo or more conductive interconnects. A plurality of the holes can meetthe opening and the conductive interconnects can extend at least withinthe opening to the respective vias.

In a particular embodiment, each conductive interconnect can overlie atleast an inner surface of the opening. The conductive interconnect canconform to a contour of the opening. In one embodiment, the conductiveinterconnects can extend along respective portions of the inner surfaceof the opening. In an exemplary embodiment, the at least one conductiveelement can include two or more conductive interconnects extending atleast within the opening. Each of the two or more conductiveinterconnects can extend to a single one of the conductive vias. In aparticular embodiment, each conductive interconnect can define aninternal space. In one embodiment, each internal space can be at leastpartially filled with a dielectric material. In an exemplary embodiment,the semiconductor assembly can also include a dielectric layer overlyingat least the inner surface of the opening. Each conductive interconnectcan fill a volume between surfaces of the dielectric layer.

In one embodiment, the semiconductor assembly can also include adielectric region disposed within the opening and an aperture extendingthrough the dielectric region. The aperture can have constant diameteror can taper in a direction towards the front surface and can have acontour not conforming to a contour of the opening. A respective one ofthe conductive interconnects can extend at least within the aperture. Inan exemplary embodiment, the respective one of the conductiveinterconnects can have a cylindrical or frusto-conical shape. In aparticular embodiment, the respective one of the conductiveinterconnects can define an internal space. In one embodiment, theinternal space can be at least partially filled with a dielectricmaterial. In an exemplary embodiment, the respective one of theconductive interconnects can fill a volume within the aperture. In aparticular embodiment, at least one of the conductive vias can overlieat least an inner surface of the respective one of the holes. Theconductive via can conform to a contour of the hole.

In an exemplary embodiment, each of the at least one of the conductivevias can define an internal space. In one embodiment, each internalspace can be at least partially filled with a dielectric material. In aparticular embodiment, the semiconductor assembly can also include adielectric layer overlying at least the inner surface of the respectiveone of the holes. Each of the at least one of the conductive vias canfill a volume between surfaces of the dielectric layer. In an exemplaryembodiment, the semiconductor assembly can also include a dielectricregion disposed within each hole and an aperture extending through eachdielectric region. The aperture can have constant diameter or can taperin a direction towards the rear surface and can have a contour notconforming to a contour of the hole. A respective one of the conductivevias can extend at least within the aperture. In a particularembodiment, the respective one of the conductive vias can have acylindrical or frusto-conical shape. In one embodiment, each of the atleast one of the conductive vias can define an internal space.

In a particular embodiment, each internal space can be at leastpartially filled with a dielectric material. In an exemplary embodiment,each of the at least one of the conductive vias can fill a volume withinthe aperture. In one embodiment, each conductive via can have a firstwidth at a top end thereof, and each conductive interconnect can have asecond width at a bottom end thereof that meets the top end of arespective one of the conductive vias, the second width being differentthan the first width. In a particular embodiment, the at least oneconductive element can include at least one conductive interconnectexposed at the rear surface for electrical connection to an externaldevice. The at least one conductive interconnect can extend within theat least one hole and at least into the opening. Each conductiveinterconnect can extend to a respective pad.

In an exemplary embodiment, the at least one conductive element caninclude two or more conductive interconnects. A plurality of the holescan meet the opening and the conductive interconnects can extend atleast within the opening and through the respective holes to therespective pads. In one embodiment, the semiconductor assembly can alsoinclude a dielectric region disposed within the hole and the opening andan aperture extending through the dielectric region. The aperture canhave a contour not conforming to either a contour of the hole or acontour of the opening. A respective one of the conductive interconnectscan extend at least within the aperture. In a particular embodiment, therespective one of the conductive interconnects can have a cylindrical orfrusto-conical shape.

In accordance with an aspect of the invention, a semiconductor assemblyincludes a semiconductor element having a front surface, a rear surfaceremote from the front surface, an opening extending from the rearsurface at least partially through the thickness of the semiconductorelement, and a hole extending from the front surface at least partiallythrough the thickness of the semiconductor element. The hole and theopening can meet at a location between the front and rear surfaces. Thesemiconductor element can further include a plurality of conductive padsat the front surface. At least one conductive pad can be laterallyoffset from the hole. The semiconductor assembly can also include atleast one conductive element having a portion exposed at the rearsurface for electrical connection with an external device. The at leastone conductive element can extend within the hole and at least into theopening. The at least one conductive element can only partially overliea surface of the respective conductive pad.

In a particular embodiment, the at least one conductive element caninclude at least one conductive interconnect exposed at the rear surfacefor electrical connection to an external device, and at least oneconductive via. The at least one conductive interconnect can extend atleast into the opening. Each via can extend within a respective hole andcan be coupled to a respective conductive interconnect and a respectivepad. In one embodiment, at least one of the conductive vias can overlieat least an inner surface of the respective one of the holes. Theconductive via can conform to a contour of the hole. In an exemplaryembodiment, each of the at least one of the conductive vias can definean internal space. In a particular embodiment, each internal space canbe at least partially filled with a dielectric material.

Further aspects of the invention provide systems which incorporatemicroelectronic structures according to the foregoing aspects of theinvention, composite chips according to the foregoing aspects of theinvention, or both in conjunction with other electronic devices. Forexample, the system may be disposed in a single housing, which may be aportable housing. Systems according to preferred embodiments in thisaspect of the invention may be more compact than comparable conventionalsystems.

BRIEF DESCRIPTION OF TEE DRAWINGS

FIG. 1 is a sectional view illustrating a via structure in accordancewith an embodiment of the invention.

FIG. 2 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIGS. 3A-3F are sectional views illustrating stages of fabrication inaccordance with the embodiments of the invention depicted in FIGS. 1 and2.

FIG. 4 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIG. 5 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIG. 6 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIGS. 7A-7J are sectional views illustrating stages of fabrication inaccordance with the embodiment of the invention depicted in FIG. 6.

FIG. 8 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIG. 9 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIG. 10 is a sectional view illustrating a stacked assembly including aplurality of packaged chips having a via structure as shown in FIG. 8.

FIG. 11 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIG. 12 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIGS. 13A-13C are sectional views illustrating stages of fabrication inaccordance with the embodiment of the invention depicted in FIG. 11.

FIG. 14 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIGS. 15A-15I are sectional views illustrating stages of fabrication inaccordance with the embodiment of the invention depicted in FIG. 14.

FIG. 16 is a sectional view illustrating a stacked assembly including aplurality of packaged chips having a via structure as shown in FIG. 14.

FIG. 17 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIGS. 18A-18G are sectional views illustrating stages of fabrication inaccordance with the embodiment of the invention depicted in FIG. 17.

FIG. 19 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIG. 20A is a corresponding top-down plan view illustrating a viastructure in accordance with the embodiment of the invention depicted inFIG. 19.

FIG. 20B is an alternate corresponding top-down plan view illustrating avia structure in accordance with the embodiment of the inventiondepicted in FIG. 19.

FIG. 20C is a perspective view illustrating a via structure including achannel-shaped opening coupled to a plurality of smaller openings inaccordance with another embodiment.

FIGS. 21A-21D are sectional views illustrating stages of fabrication inaccordance with the embodiment of the invention depicted in FIG. 19.

FIG. 22 is a sectional view illustrating a via structure in accordancewith another embodiment.

FIGS. 23A-23J are sectional views illustrating stages of fabrication inaccordance with the embodiment of the invention depicted in FIG. 22.

FIG. 24 is a sectional view illustrating a stacked assembly including aplurality of packaged chips having a via structure as shown in FIG. 22.

FIG. 25 is a schematic depiction of a system according to one embodimentof the invention.

DETAILED DESCRIPTION

FIG. 1 is a sectional view illustrating a via structure in accordancewith an embodiment of the invention. As illustrated in FIG. 1, amicroelectronic unit 10 includes a semiconductor element 20 having anopening 30 extending from a rear surface 22 partially through thesemiconductor element 20 towards a front surface 21 remote from the rearsurface. The semiconductor element 20 also has a hole 40 extendingthrough a conductive pad 50 exposed at the front surface, the hole andthe opening 30 meeting at a location between the front surface and therear surface 22. A conductive via 60 extends within the hole 40, and aconductive interconnect 80 extends within the opening 30 and has asurface 90 exposed at the rear surface that can serve as a contact forelectrical connection with an external device.

In FIG. 1, the directions parallel to front surface are referred toherein as “horizontal” or “lateral” directions; whereas the directionsperpendicular to the front surface are referred to herein as upward ordownward directions and are also referred to herein as the “vertical”directions. The directions referred to herein are in the frame ofreference of the structures referred to. Thus, these directions may lieat any orientation to the normal or gravitational frame of reference. Astatement that one feature is disposed at a greater height “above asurface” than another feature means that the one feature is at a greaterdistance in the same orthogonal direction away from the surface than theother feature. Conversely, a statement that one feature is disposed at alesser height “above a surface” than another feature means that the onefeature is at a smaller distance in the same orthogonal direction awayfrom the surface than the other feature.

The semiconductor element 20 can include a semiconductor substrate,which can be made from silicon, for example. A plurality of activesemiconductor devices (e.g., transistors, diodes, etc.) can be disposedin an active semiconductor region 23 thereof located at and/or below thefront surface 21. The plurality of active semiconductor devices can beelectrically connected to the conductive pad 50 for interconnection toother internal and/or external components. As shown in FIG. 1, an edgeof the conductive pad 50 can overlie the active semiconductor region 23,or the conductive pad can be laterally offset from the activesemiconductive region. The thickness of the semiconductor element 20between the front surface 21 and the rear surface 22 typically is lessthan 200 μm, and can be significantly smaller, for example, 130 μm, 70μm or even smaller.

The semiconductor element 20 can further include a dielectric layer 24located between the front surface 21 and the conductive pad 50. Thedielectric layer 24 electrically insulates the conductive pad 50 fromthe semiconductor element 20. This dielectric layer 24 can be referredto as a “passivation layer” of the microelectronic unit 10. Thedielectric layer 24 can include an inorganic or organic dielectricmaterial or both. The dielectric layer 24 may include anelectrodeposited conformal coating or other dielectric material, forexample, a photoimageable polymeric material, for example, a solder maskmaterial. The dielectric layer 24 may include one or more layers ofoxide material or other dielectric material.

The opening 30 extends from the rear surface 22 partially through thesemiconductor element 20 towards the front surface 21. The opening 30includes inner surface 31 that extends from the rear surface 22 throughthe semiconductor element 20 at an angle between 0 and 90 degrees to thehorizontal plane defined by the rear surface 22. The inner surface 31can have a constant slope (e.g., as shown in FIG. 1) or a varying slope(e.g., as shown in FIG. 11). For example, the angle or slope of theinner surface 31 relative to the horizontal plane defined by the rearsurface 22 can decrease in magnitude (i.e., become less positive or lessnegative) as the inner surface 31 penetrates further towards the frontsurface 21.

As shown in FIG. 1, the opening 30 has a width W1 at the rear surface 22and a width W2 at the lower surface 32 that is less than the width W1such that the opening is tapered in a direction from the rear surfacetowards the lower surface. In other examples, the opening can have aconstant width, or the opening can be tapered in a direction from thelower surface towards the rear surface. The opening 30 may extend morethan half-way from the rear surface 22 towards the front surface 21,such that a height of the opening 30 in a direction perpendicular to therear surface 22 is greater than a height of the hole 40.

The opening 30 can have any top-view shape, including for example, arectangular channel with a plurality of holes extending therefrom, asshown in FIG. 20C. In one embodiment, such as in the embodiment shown inFIG. 20A, the opening can have a round top-view shape (in FIG. 20A, theopening has a frusto-conical three-dimensional shape). In the embodimentshown in FIG. 20C, the opening has a width in a first lateral directionalong the rear surface, and the opening has a length in a second lateraldirection along the rear surface transverse to the first lateraldirection, the length being greater than the width. In some examples,the opening can have any three-dimensional shape, including for example,a cylinder, a cube, or a prism, among others.

The hole 40 can extend from a top surface 51 of the conductive pad 50(i.e., an outwardly facing surface facing away from the semiconductorelement 20), through the conductive pad to the opening 30. As shown inFIG. 1, the hole 40 has a width W3 at the lower surface 32 of theopening 30 and a width W4 at the top surface 51 of the conductive pad 50that is greater than the width W3 such that the hole is tapered in adirection from the top surface of the conductive pad towards theopening. In other examples, the hole can have a constant width, or thehole can be tapered in a direction from the opening towards the topsurface 51 of the conductive pad 50.

The inner surface 41 can have a constant slope or a varying slope. Forexample, the angle or slope of the inner surface 41 relative to thehorizontal plane defined by the front surface 21 can decrease inmagnitude (i.e., become less positive or less negative) as the innersurface 41 penetrates further from the top surface 51 of the conductivepad 50 towards the rear surface 22. The hole 40 can extend less thanhalf-way from the top surface 51 of the conductive pad 50 towards thefront surface 21, such that a height of the hole in a directionperpendicular to the front surface 21 is less than a height of theopening 30.

The hole 40 can have any top-view shape, including for example, a roundshape, as shown in FIGS. 20A-20C (in FIG. 20C, the hole has afrusto-conical three-dimensional shape). In some embodiments, the hole40 can have a square, rectangular, oval, or any other top-view shape. Insome examples, the hole 40 can have any three-dimensional shape,including for example, a cylinder, a cube, or a prism, among others.

Any number of holes 40 can extend from a single opening 30, and theholes 40 can be arranged in any geometric configuration within a singleopening 30. In one embodiment, such as in the embodiment shown in FIG.20A, there can be four holes arranged in a cluster. In anotherembodiment, such as in the embodiment shown in FIG. 20C, there can be aplurality of holes extending from a single channel-shaped openingextending along multiple axes. Particular examples of various openingand hole configurations and methods of forming these configurations aredescribed in the herein incorporated commonly owned U.S. PatentApplication Publication No. 2008/0246136, and U.S. patent applicationSer. No. 12/842,717, filed on Jul. 23, 2010.

The semiconductor element 20 includes one or more conductive pads 50exposed at or located at the front surface 21 of the semiconductorelement 20. While not specifically shown in FIG. 1, the activesemiconductor devices in the active semiconductor region 23 typicallyare conductively connected to the conductive pads 50. The activesemiconductor devices, thus, are accessible conductively through wiringincorporated extending within or above one or more dielectric layers ofthe semiconductor element 20.

In some embodiments, the conductive pads may not be directly exposed atthe front surface of the semiconductor element. Instead, the conductivepads may be electrically connected to traces or other conductiveelements extending to terminals that are exposed at the front surface ofthe semiconductor element. The conductive pads 50 can be made from anyelectrically conductive metal, including for example, copper or gold.The conductive pads 50 and any of the conductive pads disclosed hereincan have any top-view shape, including a square, round, oval, triangle,rectangle, or any other shape.

As used in this disclosure, a statement that an electrically conductiveelement is “exposed at” a surface of a dielectric element indicates thatthe electrically conductive element is available for contact with atheoretical point moving in a direction perpendicular to the surface ofthe dielectric element toward the surface of the dielectric element fromoutside the dielectric element. Thus, a terminal or other conductiveelement which is exposed at a surface of a dielectric element mayproject from such surface; may be flush with such surface; or may berecessed relative to such surface and exposed through a hole ordepression in the dielectric.

While essentially any technique usable for forming conductive elementscan be used to form the conductive elements described herein,non-lithographic techniques as discussed in greater detail in theco-pending U.S. patent application Ser. No. 12/842,669, filed on Jul.23, 2010, can be employed. Such non-lithographic techniques can include,for example, selectively treating a surface with a laser or withmechanical processes such as milling or sandblasting so as to treatthose portions of the surface along the path where the conductiveelement is to be formed differently than other portions of the surface.For example, a laser or mechanical process may be used to ablate orremove a material such as a sacrificial layer from the surface onlyalong a particular path and thus form a groove extending along the path.A material such as a catalyst can then be deposited in the groove, andone or more metallic layers can be deposited in the groove.

The conductive via 60 extends within the hole 40 and is electricallyconnected with the conductive pad 50 and the conductive interconnect 80.As shown, the conductive via 60 extends through the conductive pad 50and partially overlies and contacts the top surface 51 thereof.

As shown in FIG. 1, the conductive via 60 can fill all of the volumewithin the hole 40 inside of a dielectric layer 25 that electricallyinsulates the semiconductor element 20 from the conductive via. In otherwords, a second aperture 74 extending within the dielectric layer 25within the hole 40 conforms to a contour of the hole, and the conductivevia 60 conforms to the contour of the hole. As shown in FIG. 1, thedielectric layer 25 contacts an interior surface 53 of the conductivepad 50 exposed within the hole 40, and the dielectric layer extends outof the hole and contacts the top surface 51 of the conductive pad.

As shown in FIG. 1, the conductive via 60 is solid. In other embodiments(e.g., as shown in FIG. 2), the conductive interconnect can include aninternal space that can be left open, filled with a dielectric material,or filled with a second conductive material.

In other embodiments, such as that shown in FIG. 17, the conductive viaportion of a conductive interconnect that is located within the hole mayhave a cylindrical or frusto-conical shape. The conductive via 60 can bemade from a metal or an electrically conductive compound of a metal,including for example, copper or gold.

The conductive interconnect 80 extends within the opening 30 and iselectrically connected with the conductive via 60. As shown in FIG. 1,the conductive interconnect 80 can fill all of the volume within theopening 30 inside of a dielectric layer 70 that electrically insulatesthe semiconductor element 20 from the conductive interconnect. In otherwords, a first aperture 71 extending within the dielectric layer 70within the opening 30 conforms to a contour of the opening, and theconductive interconnect 80 conforms to the contour of the opening.

In a particular embodiment (and in all of the other embodimentsdescribed herein), the width W2 of the conductive interconnect 80 at thelower surface 32 is different from the width W3 of the conductive via 60at a top end thereof where the conductive interconnect and theconductive via meet.

As shown in FIG. 1, the conductive interconnect 80 is solid. In otherembodiments (e.g., as shown in FIG. 5), the conductive interconnect caninclude an internal space that can be left open, filled with adielectric material, or filled with a second conductive material.

In other embodiments, such as that shown in FIG. 17, the conductiveinterconnect portion of a single unitary conductive interconnect that islocated within the opening may have a cylindrical or frusto-conicalshape. The conductive interconnect 80 can be made from any electricallyconductive metal, including for example, copper or gold.

A surface 90 of the conductive interconnect 80 is exposed at the outersurface 72 of the dielectric layer 70 for interconnection to an externalelement. In one embodiment, the exposed surface 90 can be the topsurface of the interconnect 80, i.e., a surface at a furthest extent ofthe pad from the via or the exposed surface may not be a top surfacethereof. As shown, the surface 90 is located at the plane defined by theouter surface 72 of the dielectric layer 70 and above the plane definedby the rear surface 22 of the semiconductor element 20. In otherembodiments, the surface 90 of the conductive interconnect 80 can belocated above or below the plane defined by the outer surface 72 of thedielectric layer 70, and/or the surface 90 can be located at or belowthe plane defined by the rear surface 22. The surface 90 of theconductive interconnect 80 can be planarized to the outer surface 72 ofthe dielectric layer 70 or the rear surface 22, for example, by agrinding, lapping, or polishing process.

In some embodiments (e.g., the stacked embodiment shown in FIG. 10),conductive bond material can be exposed at the surface 90 or at asurface of another conductive contact exposed at the rear surface of thesemiconductor element for interconnection with an external device.

FIG. 2 is a sectional view illustrating a variation of the via structureof FIG. 1 having an alternate conductive via configuration. Themicroelectronic unit 10 a is similar to the microelectronic unit 10described above, but rather than having a conductive via that fullyfills the space inside of the hole 40 that is not occupied by thedielectric layer 25, the conductive via 60 a is deposited as a metalliclayer onto the dielectric layer, such that an internal space 27 iscreated inside the conductive via 60 a.

A method of fabricating the microelectronic unit 10 or 10 a (FIGS. 1 and2) will now be described, with reference to FIGS. 3A-3F. As illustratedin FIG. 3A, the microelectronic unit 10 or 10 a has one or more activesemiconductor regions 23 and one or more conductive pads 50. The opening30 can be formed extending downwardly from the rear surface 22 towardsthe front surface 21 of the semiconductor element 20. The opening 30 canbe formed for example, by selectively etching the semiconductor element20, after forming a mask layer where it is desired to preserve remainingportions of the rear surface 22. For example, a photoimageable layer,e.g., a photoresist layer, can be deposited and patterned to cover onlyportions of the rear surface 22, after which a timed etch process can beconducted to form the opening 30. A support wafer 12 is temporarilyattached to the front surface 21 of the semiconductor element 20 by anadhesive layer 13 to provide additional structural support to thesemiconductor element during processing of the rear surface 22.

Each opening 30 has a lower surface 32 which is flat and typicallyequidistant from the front surface 21. The inner surfaces 31 of theopening 30, extending downwardly from the rear surface 22 towards thelower surface 32, may be sloped, i.e., may extend at angles other anormal angle (right angle) to the rear surface 22, as shown in FIG. 3A.Wet etching processes, e.g., isotropic etching processes and sawingusing a tapered blade, among others, can be used to form openings 30having sloped inner surfaces 31. Laser dicing, mechanical milling,chemical etching, laser drilling, plasma etching, directing a jet offine abrasive particles towards the semiconductor element 20, amongothers, can also be used to form openings 30 (or any other hole oropening described herein) having sloped inner surfaces 31.

Alternatively, instead of being sloped, the inner surfaces of theopening 30 may extend in a vertical or substantially vertical directiondownwardly from the rear surface 22 substantially at right angles to therear surface 22. Anisotropic etching processes, laser dicing, laserdrilling, mechanical removal processes, e.g., sawing, milling,ultrasonic machining, directing a jet of fine abrasive particles towardsthe semiconductor element 20, among others, can be used to form openings30 having essentially vertical inner surfaces.

In a particular embodiment (not shown), the opening 30 can be locatedover a plurality of conductive pads 50 located on more than onemicroelectronic unit 10, such that when the microelectronic units 10 aresevered from each other, a portion of the opening 30 will be located oneach microelectronic unit 10. As used herein in the specification and inthe claims, the term “opening” can refer to a opening that is locatedentirely within a single microelectronic unit (e.g., as shown in FIGS.20A and 20B), an opening that extends across a plurality ofmicroelectronic units 10 when it is formed (not shown), or a portion ofan opening that is located on a particular microelectronic unit 10 afterit is severed from other microelectronic units 10.

After forming the opening 30 in the semiconductor element 20, aphotoimageable layer such as a photoresist or a dielectric layer 70 canbe deposited onto the rear surface 22 of the semiconductor element.Various methods can be used to form the dielectric layer 70. In oneexample, a flowable dielectric material is applied to the rear surface22 of the semiconductor element 20, and the flowable material is thenmore evenly distributed across the rear surface during a “spin-coating”operation, followed by a drying cycle which may include heating. Inanother example, a thermoplastic film of dielectric material can beapplied to the rear surface 22 of the semiconductor element 20 afterwhich the semiconductor element is heated, or is heated in a vacuumenvironment, i.e., placed in an environment under lower than ambientpressure. This then causes the film to flow downward onto the innersurfaces 31 and the lower surfaces 32 of the opening 30. In anotherexample, vapor deposition can be used to form the dielectric layer 70.

In still another example, the semiconductor element 20 can be immersedin a dielectric deposition bath to form a conformal dielectric coatingor dielectric layer 70. As used herein, a “conformal coating” is acoating of a particular material that conforms to a contour of thesurface being coated, such as when the dielectric layer 70 conforms to acontour of the opening 30 of the semiconductor element 20. Anelectrochemical deposition method can be used to form the conformaldielectric layer 70, including for example, electrophoretic depositionor electrolytic deposition.

In one example, an electrophoretic deposition technique can be used toform the conformal dielectric coating, such that the conformaldielectric coating is only deposited onto exposed conductive andsemiconductive surfaces of the assembly. During deposition, thesemiconductor device wafer is held at a desired electric potential andan electrode is immersed into the bath to hold the bath at a differentdesired potential. The assembly is then held in the bath underappropriate conditions for a sufficient time to form an electrodepositedconformal dielectric layer 70 on exposed surfaces of the device waferwhich are conductive or semiconductive, including but not limited toalong the rear surface 22 and the inner surfaces 31 and lower surface 32of the opening 30. Electrophoretic deposition occurs so long as asufficiently strong electric field is maintained between the surface tobe coated thereby and the bath. As the electrophoretically depositedcoating is self-limiting in that after it reaches a certain thicknessgoverned by parameters, e.g., voltage, concentration, etc. of itsdeposition, deposition stops.

Electrophoretic deposition forms a continuous and uniformly thickconformal coating on conductive and/or semiconductive exterior surfacesof the assembly. In addition, the electrophoretic coating can bedeposited so that it does not form on pre-existing dielectric layers,due to its dielectric (nonconductive) property. Stated another way, aproperty of electrophoretic deposition is that is does not form on alayer of dielectric material overlying a conductor provided that thelayer of dielectric material has sufficient thickness, given itsdielectric properties. Typically, electrophoretic deposition will notoccur on dielectric layers having thicknesses greater than about 10microns to a few tens of microns. The conformal dielectric layer 70 canbe formed from a cathodic epoxy deposition precursor. Alternatively, apolyurethane or acrylic deposition precursor could be used. A variety ofelectrophoretic coating precursor compositions and sources of supply arelisted in Table 1 below.

TABLE 1 ECOAT NAME POWERCRON 645 POWERCRON 648 CATHOGUARD 325MANUFACTURERS MFG PPG PPG BASF TYPE CATHODIC CATHODIC CATHODIC POLYMERBASE EPOXY EPOXY EPOXY LOCATION Pittsburgh, PA Pittsburgh, PASouthfield, MI APPLICATION DATA Pb/Pf-free Pb-free Pb or Pf-free Pb-freeHAPs, g/L 60-84 COMPLIANT VOC, g/L (MINUS WATER) 60-84 <95 CURE 20min/175 C. 20 min/175 C. FILM PROPERTIES COLOR Black Black BlackTHICKNESS, μm 10-35 10-38 13-36 PENCIL HARDNESS 2H+ 4H BATHCHARACTERISTICS SOLIDS, % wt. 20 (18-22) 20 (19-21) 17.0-21.0 pH (25 C.) 5.9 (5.8-6.2)  5.8 (5.6-5.9) 5.4-6.0 CONDUCTIVITY (25 C.) μS 1000-15001200-1500 1000-1700 P/B RATIO 0.12-0.14 0.12-0.16 0.15-0.20 OPERATIONTEMP., C. 30-34 34 29-35 TIME, sec 120-180  60-180 120+ ANODE SS316SS316 SS316 VOLTS 200-400 >100 ECOAT NAME ELECTROLAC LECTRASEAL DV494LECTROBASE 101 MANUFACTURERS MFG MACDERMID LVH COATINGS LVH COATINGSTYPE CATHODIC ANODIC CATHODIC POLYMER BASE POLYURETHANE URETHANEURETHANE LOCATION Waterbury, CT Birmingham, UK Birmingham, UKAPPLICATION DATA Pb/Pf-free Pb-free Pb-free HAPs, g/L VOC, g/L (MINUSWATER) CURE 20 min/149 C. 20 min/175 C. 20 min/175 C. FILM PROPERTIESCOLOR  Clear (+dyed) Black Black THICKNESS, μm 10-35 10-35 PENCILHARDNESS 4H BATH CHARACTERISTICS SOLIDS, % wt. 7.0 (6.5-8.0) 10-12  9-11pH (25 C.) 5.5-5.9 7-9 4.3 CONDUCTIVITY (25 C.) μS 450-600 500-800400-800 P/B RATIO OPERATION TEMP., C. 27-32 23-28 23-28 TIME, sec 60-120 ANODE SS316 316SS 316SS VOLTS 40, max  50-150

In another example, the dielectric layer can be formed electrolytically.This process is similar to electrophoretic deposition, except that thethickness of the deposited layer is not limited by proximity to theconductive or semiconductive surface from which it is formed. In thisway, an electrolytically deposited dielectric layer can be formed to athickness that is selected based on requirements, and processing time isa factor in the thickness achieved.

Thereafter, as illustrated in FIG. 3B, the conductive interconnect 80 isdeposited into the opening 30 overlying the portion of the dielectriclayer 70 that is located within the opening, such that the shape of theconductive interconnect 80 conforms to a contour of the inner surfaces31 and the lower surface 32. To form the conductive interconnect 80, anexemplary method involves depositing a metal layer by one or more ofsputtering a primary metal layer onto the outer surface 72 of thedielectric layer 70, plating, or mechanical deposition. Mechanicaldeposition can involve the directing a stream of heated metal particlesat high speed onto the surface to be coated. This step can be performedby blanket deposition onto the rear surface 22, the inner surfaces 31and the lower surfaces 32 of the opening 30, for example. In oneembodiment, the primary metal layer includes or consists essentially ofaluminum. In another particular embodiment, the primary metal layerincludes or consists essentially of copper. In yet another embodiment,the primary metal layer includes or consists essentially of titanium.One or more other exemplary metals can be used in a process to form theconductive interconnect 80. In particular examples, a stack including aplurality of metal layers can be formed on one or more of theafore-mentioned surfaces. For example, such stacked metal layers caninclude a layer of titanium followed by a layer of copper overlying thetitanium (Ti—Cu), a layer of nickel followed by a layer of copperoverlying the nickel layer (Ni—Cu), a stack of nickel-titanium-copper(Ni—Ti—Cu) provided in similar manner, or a stack of nickel-vanadium(Ni—V), for example.

The conductive interconnect 80 is insulated from the semiconductorelement 20 by the dielectric layer 70. As shown in FIG. 3B, theconductive interconnect 80 is solid. In other embodiments (e.g., FIGS. 4and 5), the conductive interconnect 80 can include an internal spacethat is filled with a second conductive material or a dielectricmaterial.

Thereafter, as illustrated in FIG. 3C, the support wafer 12 is removedfrom the front surface 21 of the semiconductor element 20, and a supportwafer 14 is temporarily attached to the rear surface 22 of thesemiconductor element 20 by an adhesive layer 15 to provide additionalstructural support to the semiconductor element during processing of thefront surface.

Thereafter, as illustrated in FIG. 3D, a mask layer (not shown) can bedeposited onto the front surface 21 and the conductive pad 50 where itis desired to preserve remaining portions of the front surface and theconductive pad. For example, a photoimageable layer, e.g., a photoresistlayer, can be deposited and patterned to cover only portions of thefront surface 21 and the conductive pad 50. Then, an etch process can beapplied to the portion of the conductive pad 50 exposed within the maskopenings so as to remove the metal of the conductive pad underlying themask opening. As a result, a hole 40 is formed that extends through theconductive pad 50 from the top surface 51 to the bottom surface 52thereof.

Thereafter, as illustrated in FIG. 3E, another etch process can beconducted in a manner that selectively etches the semiconductormaterial, e.g., silicon, thereby extending the hole 40 into thesemiconductor element from the front surface 21 to the opening 30. Aportion of the passivation layer 24 is also removed during the formationof the hole 40, and such portion can be etched through during theetching of the conductive pad 50, during etching of the semiconductorelement 20, or as a separate etching step. Etching, laser drilling,mechanical milling, or other appropriate techniques can be used toremove the portion of the passivation layer 24. In a particularembodiment, the process steps illustrated in FIGS. 3D and 3E can becombined into a single process step. For example, when forming the hole40, a laser can be used to drill through the conductive pad 50, aportion of the passivation layer 24, and a portion of the semiconductorelement 20 in a single process step. This combination of process stepsfor creating the hole 40 can be used in any of the embodiments describedherein.

Other possible dielectric layer removal techniques include variousselective etching techniques which can be isotropic or anisotropic innature. Anisotropic etch processes include reactive ion etch processesin which a stream of ions are directed towards surfaces to be etched.Reactive ion etch processes are generally less selective than isotropicetch processes such that surfaces at which ions strike at high angles ofincidence are etched to a greater extent than surfaces which areoriented with the stream of ions. When a reactive ion etch process isused, desirably, a mask layer is desirably deposited to overlie thepassivation layer 24 and an opening is formed therein which is alignedwith the hole 40. In such a way, the etch process avoids removingportions of the passivation layer 24 other than that which lies withinthe hole 40.

Thereafter, as illustrated in FIG. 3F, a photoimageable layer such as aphotoresist or a dielectric layer 25 can be deposited onto the frontsurface 21 of the semiconductor element 20 where it is desired toelectrically insulate portions of the front surface and the innersurface 41 of the hole 40 from the conductive via that will be depositedin the following step.

Thereafter, referring again to FIGS. 1 and 2, an etch process can beapplied to the portion of the dielectric layer 70 that is exposed withinthe hole 40 so as to expose the portion of the conductive interconnect80 that is aligned with the hole. Then, the conductive via 60 or 60 a isdeposited into the hole 40 overlying the portion of the dielectric layer25 that is located within the hole, for example, by blanket deposition,such that the shape of the conductive via 60 conforms to respectivecontours of the inner surface 41 of the hole, the exposed surface of theconductive pad 50, and an outer surface 26 of the dielectric layer. Theconductive via 60 or 60 a extends from the exposed portion of theconductive interconnect 80 to exposed portions of the top surface 51 andlateral surface 54 (visible in FIG. 3F) of the conductive pad 50.

As shown in FIG. 1, the conductive via 60 can be formed by continuingthe metal deposition process until the conductive via becomes solid,such that there is no open space inside of the conductive via. As shownin FIG. 2, the conductive via 60 a can be formed by stopping the metaldeposition process before the conductive via becomes solid, such thatthe internal space 27 is created inside the conductive via. Afterformation of the conductive via 60 or 60 a, the support wafer 14 isremoved from the rear surface 22 of the semiconductor element 20.

Finally, if a plurality of microelectronic units 10 or 10 a are formedtogether on a single wafer (not shown), the microelectronic units can besevered from each other along dicing lanes by sawing or other dicingmethod to form individual microelectronic units. A variety of exemplaryprocesses for severing device wafers into individual units are describedin the herein incorporated commonly owned U.S. Provisional ApplicationNos. 60/761,171 and 60/775,086, any of which can be used to sever thedevice wafers to form individual microelectronic units.

FIG. 4 is a sectional view illustrating a variation of the via structureof FIG. 1 having an alternate conductive interconnect configuration. Themicroelectronic unit 10 b is similar to the microelectronic unit 10described above, but rather than having a conductive interconnect thatfills the space inside of the opening that is not occupied by thedielectric layer, the conductive interconnect 80 b is deposited into theopening 30 as a metallic layer onto the dielectric layer 70. Theconductive interconnect 80 b is conformal to a contour of the innersurfaces 31 and the lower surface 32 of the opening 30, although theconductive interconnect is separated from the inner surfaces 31 and thelower surface 32 by the dielectric layer 70.

An internal space 28 is created inside the conductive interconnect 80 bthat is filled with a conductive mass 29, such as solder, that isexposed at the rear surface 22 for interconnection to an externaldevice. The conductive interconnect 80 b can include a contact surface90 b that extends out of the opening 30 onto the rear surface 22, andthe contact surface can serve as a contact for electrical connectionwith an external device.

In a particular embodiment, the conductive interconnect 80 b can coatthe entire outer surface 72 of the dielectric layer 70 that is locatedwithin the opening 30. Alternatively, the conductive interconnect 80 bcan coat a portion (e.g., half) of the outer surface 72 of thedielectric layer 70 that is located within the opening 30.

The conductive mass 29 can comprise a fusible metal having a relativelylow melting temperature, e.g., solder, tin, or a eutectic mixtureincluding a plurality of metals. Alternatively, the conductive mass 29can include a wettable metal, e.g., copper or other noble metal ornon-noble metal having a melting temperature higher than that of solderor another fusible metal. Such wettable metal can be joined with acorresponding feature, e.g., a fusible metal feature of an interconnectelement such as a circuit panel to externally interconnect themicroelectronic unit 10 b to such interconnect element. In a particularembodiment, the conductive mass 29 can include a conductive materialinterspersed in a medium, e.g., a conductive paste, e.g., metal-filledpaste, solder-filled paste or isotropic conductive adhesive oranisotropic conductive adhesive.

FIG. 5 is a sectional view illustrating a variation of the via structureof FIG. 4 having an alternate conductive interconnect configuration. Themicroelectronic unit 10 c is similar to the microelectronic unit 10 bdescribed above, but rather than having a internal space inside theconductive interconnect that is filled with a conductive mass, theinternal space 28 is filled with a dielectric region 75. Also, ratherthan having a conductive via that fully fills the space inside of thehole 40 that is not occupied by the dielectric layer 25, themicroelectronic unit 10 c includes the conductive via 60 a having aninternal space 27 that is shown in FIG. 2.

The dielectric region 75 can provide good dielectric isolation withrespect to the conductive interconnect 80 b. The dielectric region 75can be compliant, having a sufficiently low modulus of elasticity andsufficient thickness such that the product of the modulus and thethickness provide compliancy.

As shown in FIG. 5, the dielectric region 75 can fill the remainder ofthe opening 30 that is not occupied by the conductive interconnects 80 bor the dielectric layer 70, such that an outer surface 76 extends abovebut is parallel to a plane defined by the rear surface 22 of thesemiconductor element 20. The outer surface 76 is also located above aplane defined by the outer surface 72 of the dielectric layer 70, andthe outer surface 76 is located below a plane defined by the contactsurface 90 b of the conductive interconnect 80 b. In particularembodiments, the outer surface 76 of the dielectric region 75 can belocated at or below the planes defined by the rear surface 22 and theouter surface 72, and the outer surface can be located at or above theplane defined by the contact surface 90 b.

In another embodiment, there can be a plurality of conductiveinterconnects 80 b extending from the conductive via 60 along the innersurfaces 31 to the rear surface 22. For example, there can be fourconductive interconnects 80 b, each conductive interconnect spaced at90° intervals about a frusto-conical inner surface 31, and eachconductive interconnect having a contact surface 90 b exposed at therear surface 22 and that can serve as a contact for electricalconnection with an external device. Each conductive interconnect 80 bcan be insulated from each of the other conductive interconnects by thedielectric region 75.

In an example embodiment, wherein the opening has a channel shape (e.g.,as shown in FIG. 20C), spaced-apart conductive interconnects 80 b canalternately extend along a first inner surface 31 a defining a firstside of the channel-shaped opening and a second inner surface 31 bdefining a second side of the opening, each conductive interconnect 80 bextending from a respective conductive via 60 a.

FIG. 6 is a sectional view illustrating a variation of the via structureof FIG. 1 having an alternate conductive interconnect configuration. Themicroelectronic unit 10 d is similar to the microelectronic unit 10described above, but rather than having a conductive interconnect thatfills the space inside of the opening that is not occupied by thedielectric layer, the conductive interconnect 80 d is deposited into afirst aperture 71 formed in a dielectric region 75 d located within theopening 30.

The conductive interconnect 80 d is not conformal to either a contour ofthe inner surfaces 31 or a contour of the lower surface 32 of theopening 30. The microelectronic unit 10 d further includes a conductivecontact 90 d electrically connected to the conductive interconnect 80 d.The conductive contact 90 d can overlie an inner surface 31 of theopening 30 and may wholly overlie the inner surface 31 or the lowersurface 32 or both.

The dielectric region 75 d can provide good dielectric isolation withrespect to the conductive interconnect 80 d. The dielectric region 75 dcan be compliant, having a sufficiently low modulus of elasticity andsufficient thickness such that the product of the modulus and thethickness provide compliancy. Specifically, such a compliant dielectricregion 75 d can allow the conductive interconnect 80 d and theconductive contact 90 d attached thereto to flex or move somewhatrelative to the semiconductor element 20 when an external load isapplied to the conductive contact. In that way, the bond between theconductive contacts 90 d of the microelectronic unit 10 d and terminalsof a circuit panel (not shown) can better withstand thermal strain dueto mismatch of the coefficient of thermal expansion (“CTE”) between themicroelectronic unit and the circuit panel.

As shown in FIG. 6, the dielectric region 75 d can fill the remainder ofthe opening 30 that is not occupied by the conductive interconnect 80 dor the dielectric layer 70, such that an outer surface 76 d extends to aplane defined by the rear surface 22 of the semiconductor element 20. Inparticular embodiments, the outer surface 76 d of the dielectric region75 d can be located above or below the plane defined by the rear surface22.

The first aperture 71 is provided in the dielectric region 75 d. Thefirst aperture 71 has a frusto-conical shape and extends through thedielectric region 75 d from a bottom surface 91 of the conductivecontact 90 d to the conductive via 60. In particular embodiments, thefirst aperture can have other shapes, including for example, acylindrical shape (e.g., FIG. 8) or a combination of a cylindrical and afrusto-conical shape at different distances from the rear surface. Inthe embodiment shown, a contour of the first aperture 71 (i.e., theshape of the outer surface of the first aperture 71) does not conform toa contour of the opening 30 (i.e., the shape of the inner surface 31 ofthe opening 30).

In a particular embodiment, the conductive interconnect 80 d and theconductive via 60 can have different widths at the point where they arejoined to each other, such that an outer surface 81 of the conductiveinterconnect 80 d can have a slope discontinuity at the transition pointto an outer surface 61 of the conductive via 60.

The conductive interconnect 80 d can be formed either solid or hollowdepending upon the process conditions. Under appropriate processconditions, a conductive interconnect that includes an internal spacecan be produced, and that internal space can then be filled with adielectric material or a second conductive material, whereby thedielectric layer or the second conductive material overlies theconductive interconnect within the first aperture.

The conductive contact 90 d can be aligned with the opening 30 and canbe disposed wholly or partly within an area of the semiconductor element20 defined by the opening. As seen in FIG. 6, the conductive contact 90is wholly disposed within an area defined by the opening 30. A planedefined by an upwardly facing surface 92 of the conductive contact 90(which typically is a top surface of the contact) is substantiallyparallel to the plane defined by the rear surface 22 of thesemiconductor element 20.

As shown, the conductive contact 90 has the shape of a conductive bondpad, e.g., a thin flat member. In other embodiments, the conductivecontact can be any other type of conductive contact, including forexample, a conductive post.

As shown, the opening 30 has a first width in a lateral direction alongthe rear surface 22, and the conductive contact 90 has a second width inthe lateral direction, the first width being greater than the secondwidth.

A method of fabricating the microelectronic unit 10 d will now bedescribed, with reference to FIGS. 7A-7J. The microelectronic unit 10 dis shown in FIGS. 7A-7J as first forming the hole from the front surfaceof the semiconductor element and then forming the opening from the rearsurface thereof. The microelectronic unit 10 d and any of the other viastructures disclosed herein can be formed either by forming the holefirst (e.g., as shown in FIGS. 7A-7J) or by forming the opening first(e.g., as shown in FIGS. 3A-3F).

As illustrated in FIG. 7A, the microelectronic unit 10 d has one or moreactive semiconductor regions 23 and one or more conductive pads 50located at the front surface 21 of the semiconductor element 20. Asupport wafer (such as that shown in FIGS. 3C-3F) can be temporarilyattached to the rear surface 22 of the semiconductor element 20 toprovide additional structural support to the semiconductor elementduring processing of the front surface 21.

As illustrated in FIG. 7B, an etch process can be applied to a portionof the conductive pad 50 so as to remove a portion of the metal of theconductive pad. As a result, a hole 40 is formed that extends throughthe conductive pad 50 from the top surface 51 to the bottom surface 52thereof. The hole 40 can be formed through the conductive pad 50 asdescribed above with reference to FIG. 3D.

Thereafter, as illustrated in FIG. 7C, another etch process can beconducted in a manner that selectively etches the semiconductormaterial, e.g., silicon, thereby extending the hole 40 into thesemiconductor element 20 from the front surface 21 towards the rearsurface 22. The hole 40 can be extended into the semiconductor element20 as described above with reference to FIG. 3E.

Thereafter, as illustrated in FIG. 7D, a photoimageable layer such as aphotoresist or a dielectric layer 25 can be deposited onto the frontsurface 21 of the semiconductor element 20 and into the hole 40 asdescribed above with reference to FIG. 3F.

Thereafter, as illustrated in FIG. 7E, the conductive via 60 isdeposited into the hole 40 overlying the portion of the dielectric layer25 that is located within the hole, such that the shape of theconductive via 60 conforms to respective contours of the inner surface41 of the hole, the exposed surface of the conductive pad 50, and anouter surface 26 of the dielectric layer, as described above withreference to FIG. 1. In a particular embodiment, the conductive via canbe formed having an internal space therein, such as the conductive via60 a shown in FIG. 2. After formation of the conductive via 60, thesupport wafer (not shown in FIGS. 7A-7E) can be removed from the rearsurface 22 of the semiconductor element 20.

Thereafter, as illustrated in FIG. 7F, a support wafer 12 is temporarilyattached to the front surface 21 of the semiconductor element 20 by anadhesive layer 13 to provide additional structural support to thesemiconductor element during processing of the rear surface 22.

Thereafter, as illustrated in FIG. 7G, the thickness of thesemiconductor element 20 between the front surface 21 and the rearsurface 22 can be reduced. Grinding, lapping, or polishing of the rearsurface or a combination thereof can be used to reduce the thickness.During this step, as an example, the initial thickness T1 (shown in FIG.7F) of the semiconductor element 20 can be reduced from about 700 μm toa thickness T2 (shown in FIG. 7G) of about 130 μm or less.

Thereafter, as illustrated in FIG. 7I, the opening 30 can be formedextending downwardly from the rear surface 22 to the hole 40, asdescribed above with reference to FIG. 3A. An etch process can beapplied to the portion of the dielectric layer 25 that is exposed withinthe opening 30 so as to expose the portion of the conductive via 60 thatis aligned with the hole.

Thereafter, as illustrated in FIG. 7I, the dielectric region 75 d can beformed inside the opening 30. Optionally, the dielectric region 75 d canbe formed such that an exposed outer surface 76 d of the region isco-planar or substantially co-planar with the rear surface 22 of thesemiconductor element an exposed surface of a dielectric layer coatingthe rear surface. For example, a self-planarizing dielectric materialcan be deposited in the opening 30, e.g., by a dispensing or stencilingprocess. In another example, a grinding, lapping, or polishing processcan be applied to the rear surface 22 of the semiconductor element 20after forming the dielectric region 75 d to planarize the outer surface76 d of the dielectric region to the rear surface 22.

Thereafter, as illustrated in FIG. 7J, the first aperture 71 is formed,extending through the dielectric region 75 d between the outer surface76 d of the dielectric region and the conductive via 60. The firstaperture 71 can be formed, for example, via laser ablation, or any otherappropriate method. The conductive interconnect 80 d can be formedwithin the first aperture 71. The conductive interconnect 80 d can beelectrically connected to the conductive via 60 and insulated from thesemiconductor element 20 by the dielectric region 75 d. Then, theconductive contact 90 d can be formed. The conductive contact 90 d isexposed at the outer surface 76 d of the dielectric region 75 d forinterconnection with an external device. The conductive contact 90 d iselectrically connected to the conductive interconnect 80 d at the bottomsurface 91 thereof. In some embodiments, the conductive interconnect 80d and the conductive contact 90 d can be formed during a singleelectroless deposition step. In other embodiments, the conductiveinterconnect 80 d and the conductive contact 90 d can be formed byseparate electroless deposition steps. After formation of the conductiveinterconnect 80 d and the conductive contact 90 d, the support wafer canbe removed from the front surface 21 of the semiconductor element 20.

Finally, if a plurality of microelectronic units 10 d are formedtogether on a single wafer (not shown), the microelectronic units can besevered from each other along dicing lanes by sawing or other dicingmethod to form individual microelectronic units.

FIG. 8 is a sectional view illustrating a variation of the via structureof FIG. 6 having an alternate conductive interconnect configuration. Themicroelectronic unit 10 e is similar to the microelectronic unit 10 ddescribed above, but rather than having a conductive interconnect havinga frusto-conical shape, the conductive interconnect 80 e has acylindrical shape.

FIG. 9 is a sectional view illustrating a variation of the via structureof FIG. 8 having an alternate conductive via configuration. Themicroelectronic unit 10 f is similar to the microelectronic unit 10 edescribed above, but rather than having a conductive via that fullyfills the space inside of the hole that is not occupied by a dielectriclayer, the conductive via 60 f is deposited as a metallic layer onto thedielectric layer 25, such that an internal space 27 is created insidethe conductive via 60 f. As shown in FIG. 9, an edge 98 of theconductive contact 90 f (or any of the conductive contacts disclosedherein) can overlie the rear surface 22 of the semiconductor element 20,or an edge 99 of the conductive contact (or any of the conductivecontacts disclosed herein) can overlie the opening 30. In one embodiment(e.g., as shown in FIG. 8), the entire conductive contact can overliethe opening 30.

FIG. 10 is a sectional view illustrating a stacked assembly including aplurality of packaged chips having a via structure as shown in FIG. 8.In the embodiment shown, a stacked assembly 100 includes a plurality ofmicroelectronic units 10 e electrically connected to one another.Although FIG. 10 includes a plurality of microelectronic units 10 e asshown in FIG. 8, any of the microelectronic units disclosed herein canbe stacked to form a stacked assembly. Although FIG. 10 shows a stackedplurality of microelectronic units 10 e, in a particular embodiment, thestacked assembly 100 (or any of the stacked assemblies disclosed herein)may be a portion of a stacked plurality of semiconductor wafers, eachwafer containing a plurality of laterally adjacent microelectronic units10 e. Such a stacked wafer assembly can include a plurality of stackedassemblies 100, and the stacked assemblies 100 can be separated from oneanother by dicing lanes extending therebetween. The stacked assemblies100 can be detached from one another, for example, by cutting along thedicing lanes with a laser.

By providing front surface conductive pads 50 and rear surfaceconductive contacts 90 e in each microelectronic unit 10 e, severalmicroelectronic units can be stacked one on top of the other to form astacked assembly 100 of microelectronic units. In such arrangement, thefront surface conductive pads 50 are aligned with the rear surfaceconductive contacts 90 e. Connection between respective adjacent ones ofthe microelectronic units in the stacked assembly is through conductivemasses 102. The dielectric layer 25 on the front surface 21 and adielectric region 104 extending between the dielectric layer and therear surface 22 provide electrical isolation between adjacentmicroelectronic units 10 e in the stacked assembly 100 except whereinterconnection is provided.

FIG. 11 is a sectional view illustrating a variation of the viastructure of FIG. 5 having an alternate conductive interconnectconfiguration. The microelectronic unit 10 g is similar to themicroelectronic unit 10 c described above, but rather than having aconductive interconnect that is filled with a dielectric region havingan exposed outer surface, the microelectronic unit 10 g has a conductiveinterconnect 80 g that is filled with a dielectric region 75 g that issurrounded by the conductive interconnect and a conductive contact 90 gthat is exposed at the rear surface 22 g for connection with an externaldevice. Also, rather than having a conductive via having an internalspace, the microelectronic unit 10 g includes a conductive via 60 thatfully fills the space inside of the hole 40 as shown in FIG. 1.Additionally, the opening 30 g has inner surfaces 31 that have a varyingslope as the inner surfaces penetrate into the microelectronic element20 g from the rear surface 22 to a lower surface 32.

FIG. 12 is a sectional view illustrating a variation of the viastructure of FIG. 11 having an alternate conductive via configuration.The microelectronic unit 10 h is similar to the microelectronic unit 10g described above, but rather than having a conductive via that fullyfills the space inside of the hole 40 that is not occupied by thedielectric layer 25, the microelectronic unit 10 h has a conductive via60 a including an internal space 27, as shown in FIG. 2.

A method of fabricating the microelectronic unit 10 g will now bedescribed, with reference to FIGS. 13A-13C. The microelectronic unit 10g is shown in FIGS. 13A-13C as first forming the hole from the frontsurface of the semiconductor element and then forming the opening fromthe rear surface thereof, similar to the method shown in FIGS. 7A-7J.

Before the stage of fabrication shown in FIG. 13A, the microelectronicunit 10 g can undergo the same stages of fabrication shown in FIGS.7A-7G. Thereafter, as illustrated in FIG. 13A, the opening 30 g can beformed extending downwardly from the rear surface 22 g to the hole 40,as described above with reference to FIG. 7H. An etch process can beapplied to the portion of the dielectric layer 25 that is exposed withinthe opening 30 g so as to expose the portion of the conductive via 60that is aligned with the hole.

Thereafter, as illustrated in FIG. 13B, a photoimageable layer such as aphotoresist or a dielectric layer 70 g can be deposited onto the rearsurface 22 g of the semiconductor element 20 g and in the opening 30 g,as described above with reference to FIG. 3A.

Thereafter, as illustrated in FIG. 13C, the conductive interconnect 80 gis deposited as a metallic layer onto the dielectric layer 70 g withinthe opening 30 g, such that an internal space 85 is created inside theconductive interconnect. As described with reference to FIG. 3B, anexemplary method involves depositing a metal layer by one or more ofsputtering a primary metal layer onto the outer surface 72 g of thedielectric layer 70 g, plating, or mechanical deposition.

Then, the internal space 85 can be filled with a dielectric region 75 g,as described with reference to FIG. 7I. Optionally, the dielectricregion 75 g can be formed such that an exposed outer surface of theregion is co-planar or substantially co-planar with the rear surface 22g of the semiconductor element an exposed surface 72 g of the dielectriclayer 70 g.

Then, the conductive contact 90 g can be formed. The conductive contact90 g is exposed at the outer surface of the dielectric region 75 g forinterconnection with an external device. The conductive contact 90 g iselectrically connected to the upper edges of the conductive interconnect80 g at the bottom surface 91 g thereof. After formation of theconductive interconnect 80 g and the conductive contact 90 g, thesupport wafer 12 can be removed from the front surface 21 g of thesemiconductor element 20 g.

FIG. 14 is a sectional view illustrating a variation of the viastructure of FIG. 5 having an alternate conductive interconnectconfiguration. The microelectronic unit 10 i is similar to themicroelectronic unit 10 c described above, but rather than having aconductive interconnect that coats the entire outer surface of thedielectric layer that is located within the opening, the microelectronicunit 10 i has a conductive interconnect 80 i that has the shape of atrace that only coats a portion of the outer surface 72 of thedielectric layer 70 that is located within the opening 30. Also, theconductive contact 90 i has the shape of a trace that extends along theportion of the outer surface 72 of the dielectric layer 70 that coatsthe rear surface 22 of the semiconductor element 20 not overlying theopening 30. Also, rather than having a conductive via having an internalspace, the microelectronic unit 10 i includes a conductive via 60 thatfully fills the space inside of the hole 40 as shown in FIG. 1.

A method of fabricating the microelectronic unit 10 i will now bedescribed, with reference to FIGS. 15A-15I. The microelectronic unit 10i is shown in FIGS. 15A-15I as first forming the hole from the frontsurface of the semiconductor element and then forming the opening fromthe rear surface thereof, similar to the method shown in FIGS. 7A-7J.

As shown in FIGS. 15A-15G, the microelectronic unit 10 i can undergo thesame stages of fabrication shown in FIGS. 7A-7G, although the hole 40formed during the stages shown in FIGS. 15A and 15B is formed leavingsufficient room on the rear surface 22 of the semiconductor element 20to allow for the formation of the trace-shaped conductive contact 90 ithat does not overlay (i.e., is laterally offset from) the opening 30.

Thereafter, as illustrated in FIG. 15E, the opening 30 can be formedextending downwardly from the rear surface 22 to the hole 40, asdescribed above with reference to FIG. 7H. Then, a photoimageable layersuch as a photoresist or a dielectric layer 70 can be deposited onto therear surface 22 of the semiconductor element 20 and in the opening 30,as described above with reference to FIG. 13B.

Thereafter, as illustrated in FIG. 15I, an etch process can be appliedto the portion of the dielectric layer 70 that overlies the hole 40 andthe portion of the dielectric layer 25 that is exposed within theopening 30 so as to expose the portion of the conductive via 60 that isaligned with the hole.

Then, a trace-shaped conductive interconnect 80 i and a trace-shapedconductive contact 90 i can be deposited as a metallic layer onto thedielectric layer 70 within the opening 30 (the conductive interconnect)and extending along the rear surface 22 (the conductive contact),respectively. An exemplary method of forming the conductive interconnect80 i and the conductive contact 90 i can be a non-lithographic techniquesuch as selectively treating a surface with a laser. The conductivecontact 90 i is exposed at the outer surface 72 of the dielectric layer70 for interconnection with an external device. The conductive contact90 i is laterally offset from (i.e., does not vertically overlie) theconductive pad 50.

Thereafter, referring again to FIG. 14, the remaining space within theopening 30 not occupied by the conductive interconnect 80 i can befilled with a dielectric region 75 i, as described with reference toFIG. 7I. Optionally, the dielectric region 75 i can be formed such thatan exposed outer surface 76 i of the region is co-planar orsubstantially co-planar with the exposed surface 72 i of the dielectriclayer 70 i. After formation of the dielectric region 75 i, the supportwafer 12 can be removed from the front surface 21 of the semiconductorelement 20.

FIG. 16 is a sectional view illustrating a stacked assembly including aplurality of packaged chips having a via structure as shown in FIG. 14.In the embodiment shown, a stacked assembly 110 includes a plurality ofmicroelectronic units 10 i electrically connected to one another.

Similar to FIG. 10, several microelectronic units 10 i can be stackedone on top of the other to form a stacked assembly 110 ofmicroelectronic units. Because in a particular microelectronic unit 10i, the conductive contact 90 i does not vertically overlie theconductive pad 50, each adjacent pair of microelectronic units ispositioned with the respective openings 30 and holes 40 offset such thatthe conductive pad 50 of an upper microelectronic unit overlies theconductive contact 90 i of a lower microelectronic unit.

In such arrangement, similar to FIG. 10, connection between respectiveadjacent ones of the microelectronic units in the stacked assembly isthrough conductive masses 112. The dielectric layer 25 on the frontsurface 21 and a dielectric region 114 extending between the dielectriclayer and the rear surface 22 provide electrical isolation betweenadjacent microelectronic units 10 i in the stacked assembly 110 exceptwhere interconnection is provided.

FIG. 17 is a sectional view illustrating a variation of the viastructure of FIG. 8 having an alternate conductive via configuration.The microelectronic unit 10 j is similar to the microelectronic unit 10e described above, but rather than having a conductive via beingconformal to a dielectric layer located within the hole, themicroelectronic unit 10 j includes a conductive via portion 60 j of aconductive interconnect 78 extending through and non-conformal to adielectric region 65 located within the hole 40.

The microelectronic unit 10 j includes a single unitary conductiveinterconnect 78 extending between the conductive pad 50 j and theconductive contact 90 j. The conductive interconnect 78 includes aconductive interconnect portion 80 j extending from the conductivecontact 90 j through the opening 30 and a conductive via portion 60 jextending from the conductive interconnect portion to the conductive pad50 j through the hole 40. The conductive interconnect 78 extends throughan aperture 71 j extending through the dielectric regions 75 j and 65.The aperture 71 j and the conductive interconnect 78 do not conform to acontour of either the opening 30 or the hole 40.

As shown in FIG. 17, a dielectric region 75 j can fill the remainder ofthe opening 30 that is not occupied by the conductive interconnectportion 80 j, such that an outer surface 76 j extends above but isparallel to a plane defined by the rear surface 22 of the semiconductorelement 20. The dielectric region 65 can fill the remainder of theopening 40 that is not occupied by the conductive via portion 60 j.

In a particular embodiment (not shown), the microelectronic unit 10 jcan include a single unitary dielectric region that fills the remainderof the opening 30 and the hole 40 that is not occupied by the conductiveinterconnect 78. Alternatively, such a single dielectric region caninclude two or more layers of material.

In the embodiment shown in FIG. 17, the degree of compliancy provided bythe product of the thickness of the dielectric region 75 j and itsmodulus of elasticity can be sufficient to compensate for strain appliedto the conductive contact 90 j due to thermal expansion mismatch betweenthe microelectronic unit 10 j and a substrate to which themicroelectronic unit is mounted through the conductive contact. Anunderfill (not shown) can be provided between the exposed outer surface76 j of the dielectric region and such circuit panel to enhanceresistance to thermal strain due to CTE mismatch.

A method of fabricating the microelectronic unit 10 j will now bedescribed, with reference to FIGS. 18A-18G. As illustrated in FIG. 18A,the opening 30 can be formed extending downwardly from the rear surface22 towards the front surface 21 of the semiconductor element 20, in amanner similar to that described above with respect to FIG. 3A. Asupport wafer 12 is temporarily attached to the front surface 21 of thesemiconductor element 20 by an adhesive layer 13 to provide additionalstructural support to the semiconductor element during processing of therear surface 22.

Thereafter, as illustrated in FIG. 18B, the dielectric region 75 j canbe formed inside the opening 30, in a manner similar to that describedabove with respect to FIG. 7I. Optionally, the dielectric region 75 jcan be formed such that an exposed outer surface 76 j of the region isco-planar or substantially co-planar with the rear surface 22 of thesemiconductor element 20.

Thereafter, as illustrated in FIGS. 18C-18E, the microelectronic unit 10j can undergo the same stages of fabrication shown in FIGS. 3C-3E toform the hole 40 extending through the conductive pad 50 and into thesemiconductor element 20. As described above with reference to FIGS. 3Dand 3E, the process steps shown in FIGS. 18D and 18E can be combinedinto a single process step, thereby forming the hole 40 in such singlestep with a laser.

Thereafter, as illustrated in FIG. 18F, the dielectric region 65 can beformed inside the hole 40, in a manner similar to that described abovewith respect to FIG. 7I. The dielectric region 65 can extend through thesemiconductor element 20 to meet a portion of the dielectric region 75 jthat is exposed within the hole 40. Optionally, the dielectric region 65can be formed such that an exposed outer surface 66 of the region isco-planar or substantially co-planar with the top surface 51 of theconductive pad 50. In a particular embodiment (not shown), thedielectric region 65 can extend out of the hole 40 onto the top surface51 of the conductive pad 50, similar to how the dielectric layer 25shown in FIG. 1 extends out of the hole onto the top surface of theconductive pad.

Thereafter, as illustrated in FIG. 18G, a single aperture 71 j iscreated extending through the dielectric regions 75 j and 65 from theouter surface 76 j to the outer surface 66, for example via laserablation or mechanical drilling. In a particular embodiment, the hole 40and the aperture 71 j can be formed in a single process step using alaser, thereby combining the process steps shown in FIGS. 18D, 18E, and18G. In such an embodiment, a dielectric layer or region coating theexposed inner surface 41 of the hole 40 such as the dielectric region 65can be formed (e.g., as shown in FIG. 18F) after the formation of thehole 40 and the aperture 71 j.

Thereafter, referring again to FIG. 17, the conductive interconnect 78is created by plating an interior surface of the aperture 71 with aconductive metal such as copper or gold. Similar to the conductiveinterconnect 80 d shown in FIG. 6, the conductive interconnect 78 may besolid or may contain an internal space that is left open or filled witha dielectric material. Preferably, the conductive interconnect 78 isplated onto an interior surface of the aperture 71 as well as the topsurface 51 of the conductive pad 50, resulting in a thicker conductivepad 50 j having at least two layers of metal.

Then, the conductive contact 90 j can be formed. The conductive contact90 j is exposed at the outer surface 76 j of the dielectric region 75 jfor interconnection with an external device. In some embodiments, theconductive interconnect 78 and the conductive contact 90 j can be formedduring a single electroless deposition step. In other embodiments, theconductive interconnect 78 and the conductive contact 90 j can be formedby separate electroless deposition steps. After formation of theconductive interconnect 78 and the conductive contact 90 j, the supportwafer can be removed from the front surface 21 of the semiconductorelement 20.

FIG. 19 is a sectional view illustrating a via structure in accordancewith another embodiment having a plurality of holes extending to asingle opening. As illustrated in FIG. 19, a microelectronic unit 210includes a semiconductor element 220 having an opening 230 extendingfrom a rear surface 222 partially through the semiconductor element 220towards a front surface 221 remote from the rear surface. Thesemiconductor element 220 also has a plurality of holes 240 extendingthrough respective conductive pads 250 exposed at the front surface 221,each of the holes 240 meeting the single opening 230 at a locationbetween the front surface and the rear surface 222. A respectiveconductive via 260 extends within each hole 240, and a respectiveconductive interconnect 280 extends from each conductive via within theopening 230 to a respective conductive contact 290 exposed at the rearsurface 222 for electrical connection with an external device.

As shown in FIG. 19, each conductive via 260 can fill all of the volumewithin a respective hole 240 inside of a dielectric layer 267 thatelectrically insulates the semiconductor element 220 from the conductivevia. The conductive interconnects 280 extend along an outer surface 272of a dielectric layer 270 that is conformal to inner surfaces 231 and alower surface 232 of the opening 230, such that the conductiveinterconnects are conformal to a contour of the opening.

The semiconductor element 220 can further include a dielectric layer 224(e.g., a passivation layer) located between the front surface 221 andthe conductive pads 250. A dielectric region 275 can fill the remainderof the opening 230 that is not occupied by the conductive interconnects280 or the dielectric layer 270, such that an outer surface 276 extendsabove but is parallel to a plane defined by the rear surface 222 of thesemiconductor element 220.

The microelectronic element 210 can have various combinations of holes40 extending to a single opening 30. For example, FIG. 20A illustrates amicroelectronic unit 210 a that can be one potential top-down plan viewof the microelectronic unit 210 shown in FIG. 19. As shown in FIG. 20A,the microelectronic element 210 a includes four holes 240 extending to asingle opening 230 having a substantially round top-view shape. Eachhole 240 extends through a corner of a corresponding square-shapedconductive pad 250 to the opening 230.

FIG. 20B illustrates a microelectronic unit 210 b that can be anotherpotential top-down plan view of the microelectronic unit 210 shown inFIG. 19. As shown in FIG. 20B, the microelectronic element 210 bincludes two holes 240 extending to a single opening 230 having asubstantially oval top-view shape. Each hole 240 extends through a sideof a corresponding square-shaped conductive pad 250 to the opening 230.

FIG. 20C illustrates a semiconductor element 220 c that can be apotential perspective view of the semiconductor element 220 included inthe microelectronic unit 210 shown in FIG. 19. The semiconductor element220 c includes a plurality of holes 240 extending to a single opening230 having a channel shape extending in a plurality of lateraldirections perpendicular to a thickness of the semiconductor element. Arow of holes 240 extends along each lateral direction defined bychannel-shaped opening 230. In a particular embodiment, the opening 230can have having a length extending in a first direction along a surfaceof the semiconductor element 220, and a width extending a second lateraldirection transverse to said first direction, the length being greaterthan the width.

A method of fabricating the microelectronic unit 210 shown in FIG. 19will now be described, with reference to FIGS. 21A-21D. Themicroelectronic unit 210 is shown in FIGS. 21A-21D as first havingformed the opening from the front surface of the semiconductor elementand then forming the holes from the rear surface thereof, similar to themethod shown in FIGS. 3A-3F.

Before the stage of fabrication shown in FIG. 21A, the microelectronicunit 210 can undergo similar stages of fabrication shown in FIGS.13A-13C, wherein: (i) an opening is formed extending from the frontsurface of the semiconductor element, (ii) interior surfaces of theopening are coated with a conformal dielectric layer, (iii) a conformalconductive interconnect is plated onto an outer surface of thedielectric layer, (iv) a dielectric region is filled into the remainingportion of the opening not occupied by the dielectric layer or theconductive interconnect, (v) a conductive contact is plated onto theouter surface of the dielectric region, and (vi) the front surface ofthe semiconductor element is coated with a conformal dielectric layer.

As illustrated in FIG. 21A, the microelectronic unit 210 includes twoconductive interconnects 280, each conductive interconnect extendingfrom a respective conductive contact 290 to a lower surface 232 of theopening 230, such that a lower end 283 of each conductive interconnect280 overlies a portion of a respective conductive pad 250. A dielectriclayer 225 has been deposited onto the front surface 221 of thesemiconductor element 220 and onto the top surface 251 of eachconductive pad 250.

Thereafter, as illustrated in FIG. 21B, an etch process can be appliedto a portion of the dielectric layer 225, leaving remaining portions ofthe dielectric layer on the front surface 221 where it is desired toelectrically insulate portions of the front surface conductive vias 260that will be deposited later. As shown, a portion of the top surface 251of each conductive pad 250 remains coated by the dielectric layer 225.In a particular embodiment, the entire top surface 251 of eachconductive pad 250 can be exposed within the openings created in thedielectric layer 225.

Thereafter, as illustrated in FIG. 21C, an etch process can be appliedto a portion of each conductive pad 250 so as to remove a portion of themetal of the conductive pad. As a result, a hole 240 is formed thatextends through each conductive pad 250 from the top surface 251 to thebottom surface 252 thereof. Each hole 240 can be formed through therespective conductive pad 250 as described above with reference to FIG.3D.

Thereafter, as illustrated in FIG. 21D, another etch process can beconducted in a manner that selectively etches the semiconductormaterial, e.g., silicon, thereby extending the holes 240 into thesemiconductor element 220 from the front surface 221 towards the rearsurface 222, thereby exposing the lower ends 283 of the respectiveconductive interconnects 280. The holes 240 can be extended into thesemiconductor element 220 as described above with reference to FIG. 3E.Then, a dielectric layer 267 can be deposited onto the inner surface 241of each respective hole 240 as described above with reference to FIG.3F. As shown in FIG. 21D, the dielectric layer 267 extends between thedielectric layer 270 exposed at each hole 240 and the passivation layer224. In a particular embodiment, the dielectric layer 267 can extendcompletely through the conductive pad 250, contacting an interiorsurface 253 of the conductive pad exposed within the hole 240, and thedielectric layer 267 can extends out of the hole and contact the topsurface 251 of the conductive pad.

Thereafter, referring again to FIG. 19, the conductive vias 260 can bedeposited into the respective holes 240 overlying the dielectric layers267 and 225, for example, by blanket deposition, such that the shape ofeach conductive via 260 conforms to respective contours of the innersurface 241 of the hole, the exposed surface of the conductive pad 250,and an outer surface 226 of the dielectric layer 225. Each conductivevia 260 extends from the exposed lower end 283 of the respectiveconductive interconnect 280 to exposed portions of the top surface 251and interior surface 253 (visible in FIG. 21D) of the conductive pad250.

FIG. 22 is a sectional view illustrating a variation of the viastructure of FIG. 14 having an alternate conductive pad and conductivevia configuration. The microelectronic unit 10 k is similar to themicroelectronic unit 10 i described above with respect to FIG. 14, butrather than having a hole penetrating through a conductive pad at leastpartially overlying the opening, the hole 40 k and the opening 30 k arecreated at locations that are laterally offset from the conductive pad50 k. A conductive trace 68 extends along the front surface 21 of theconductive element 20 k to electrically connect the conductive via 60 kwith the conductive pad 50 k. Also, rather than having a solidconductive via, the microelectronic unit 10 k includes a conductive via60 k having an internal space such as that shown in FIG. 2.

A method of fabricating the microelectronic unit 10 k will now bedescribed, with reference to FIGS. 23A-23J. The microelectronic unit 10k is shown in FIGS. 23A-23J as first forming the hole from the frontsurface of the semiconductor element and then forming the opening fromthe rear surface thereof, similar to the method shown in FIGS. 15A-15I.

As illustrated in FIG. 23A, the microelectronic unit 10 k has one ormore conductive pads 50 k located at the front surface 21 of thesemiconductor element 20 k. A support wafer (such as that shown in FIGS.3C-3F) can be temporarily attached to the rear surface 22 of thesemiconductor element 20 k to provide additional structural support tothe semiconductor element during processing of the front surface 21.

Thereafter, as illustrated in FIG. 23B, a portion of the passivationlayer 24 can be removed at a location where it is desired to form thehole 40 k, the location being laterally offset from the conductive pad50 k

Thereafter, as illustrated in FIG. 23C, another etch process can beconducted in a manner that selectively etches the semiconductormaterial, e.g., silicon, thereby forming the hole 40 k into thesemiconductor element 20 k from the front surface 21 towards the rearsurface 22. The hole 40 k is formed at a location that is laterallyoffset from the conductive pad 50 k. The hole 40 k can be etched intothe semiconductor element 20 as described above with reference to FIG.3E.

Thereafter, as illustrated in FIG. 23D, a photoimageable layer such as aphotoresist or a dielectric layer 25 k can be deposited onto the frontsurface 21 of the semiconductor element 20 and into the hole 40 k asdescribed above with reference to FIG. 3F.

Thereafter, as illustrated in FIG. 23E, the conductive via 60 k isdeposited into the hole 40 k overlying the portion of the dielectriclayer 25 k that is located within the hole, such that the shape of theconductive via 60 k conforms to respective contours of the inner surface41 k of the hole. The conductive via 60 k can be formed having aninternal space therein, similar to as the conductive via 60 a shown inFIG. 2. The conductive contact 68 can be formed, extending between theconductive via 60 k and the conductive pad 50 k along the front surface21. In a particular embodiment, the conductive via 60 k and theconductive trace 68 can be formed during a single electroless depositionstep.

Thereafter, as illustrated in FIG. 23F, a photoimageable layer such as aphotoresist or a dielectric layer 124 can be deposited onto the frontsurface 21 of the semiconductor element 20 k and onto portions of theconductive via 60 k, the conductive trace 68, and/or the conductive pad50 k to provide electrical isolation between adjacent microelectronicunits 10 k, for example, in a stacked assembly such as that shown inFIG. 24. After formation of the dielectric layer 124, a support wafer(if used) can be removed from the front surface 21 of the semiconductorelement 20.

Thereafter, as illustrated in FIG. 23G, a support wafer 12 istemporarily attached to the front surface 21 of the semiconductorelement 20 k by an adhesive layer 13 to provide additional structuralsupport to the semiconductor element during processing of the rearsurface 22.

Thereafter, as illustrated in FIG. 23E, the thickness of thesemiconductor element 20 k between the front surface 21 and the rearsurface 22 can be reduced as described with reference to FIGS. 7F and7G. During this step, as an example, the initial thickness T3 (shown inFIG. 23G) of the semiconductor element 20 k can be reduced to athickness T4 (shown in FIG. 23H).

Thereafter, as illustrated in FIG. 23I, the opening 30 k can be formedextending downwardly from the rear surface 22 to the hole 40 k, asdescribed above with reference to FIG. 7H. Then, a photoimageable layersuch as a photoresist or a dielectric layer 70 k can be deposited ontothe rear surface 22 of the semiconductor element 20 k and in the opening30 k, as described above with reference to FIG. 13B.

Thereafter, as illustrated in FIG. 23J, an etch process can be appliedto the portion of the dielectric layer 70 k that overlies the hole 40 kand the portion of the dielectric layer 25 k that is exposed within theopening 30 k so as to expose the portion of the conductive via 60 k thatis aligned with the hole.

Then, a trace-shaped conductive interconnect 80 k and a trace-shapedconductive contact 90 k can be deposited as a metallic layer onto thedielectric layer 70 k within the opening 30 k (the conductiveinterconnect) and extending along the rear surface 22 (the conductivecontact), respectively, as described above with reference to FIG. 15I.The conductive contact 90 k is exposed at the outer surface 72 of thedielectric layer 70 k for interconnection with an external device orwith another microelectronic unit 10 k in a stacked assembly. Theconductive contact 90 k is laterally offset from the opening 30 k andthe hole 40 k, but the conductive contact is vertically aligned with(i.e., overlying) the conductive pad 50 k.

Thereafter, referring again to FIG. 22, the remaining space within theopening 30 k not occupied by the conductive interconnect 80 k or thedielectric layer 70 k can be filled with a dielectric region 75 k, asdescribed with reference to FIG. 7I. After formation of the dielectricregion 75 k, the support wafer 12 can be removed from the front surface21 of the semiconductor element 20 k.

FIG. 24 is a sectional view illustrating a stacked assembly including aplurality of packaged chips having a via structure as shown in FIG. 22.In the embodiment shown, a stacked assembly 120 includes a plurality ofmicroelectronic units 10 k electrically connected to one another.

Similar to FIG. 16, several microelectronic units 10 k can be stackedone on top of the other to form a stacked assembly 120 ofmicroelectronic units. Because in a particular microelectronic unit 10k, the conductive contact 90 k vertically overlies the conductive pad 50k, each adjacent pair of microelectronic units can be positioned withthe respective openings 30 k and holes 40 k vertically aligned such thatthe conductive pad 50 k of an upper microelectronic unit overlies theconductive contact 90 k of a lower microelectronic unit.

In such arrangement, similar to FIG. 16, connection between respectiveadjacent ones of the microelectronic units in the stacked assembly isthrough conductive masses 122. The dielectric layer 124 at the frontsurface 21 and the dielectric region 75 k at the rear surface 22 provideelectrical isolation between adjacent microelectronic units 10 k in thestacked assembly 120 except where interconnection is provided. Anadhesive layer 126 located between the front surface 21 of an uppermicroelectronic unit 10 k and the lower surface 22 of a lowermicroelectronic unit can bond adjacent microelectronic units 10 ktogether.

The methods disclosed herein for forming via structures in semiconductorelements can be applied to a microelectronic substrate, such as a singlesemiconductor chip, or can be applied simultaneously to a plurality ofindividual semiconductor chips which can be held at defined spacings ina fixture or on a carrier for simultaneous processing. Alternatively,the methods disclosed herein can be applied to a microelectronicsubstrate or element including a plurality of semiconductor chips whichare attached together in form of a wafer or portion of a wafer toperform processing as described above simultaneously with respect to aplurality of semiconductor chips on a wafer-level, panel-level orstrip-level scale.

The structures discussed above provide extraordinary three-dimensionalinterconnection capabilities. These capabilities can be used with chipsof any type. Merely by way of example, the following combinations ofchips can be included in structures as discussed above: (i) a processorand memory used with the processor; (ii) plural memory chips of the sametype; (iii) plural memory chips of diverse types, such as DRAM and SRAM;(iv) an image sensor and an image processor used to process the imagefrom the sensor; (v) an application-specific integrated circuit (“ASIC”)and memory.

The structures discussed above can be utilized in construction ofdiverse electronic systems. For example, a system 300 in accordance witha further embodiment of the invention includes a structure 306 asdescribed above in conjunction with other electronic components 308 and310. In the example depicted, component 308 is a semiconductor chipwhereas component 310 is a display screen, but any other components canbe used. Of course, although only two additional components are depictedin FIG. 25 for clarity of illustration, the system may include anynumber of such components. The structure 306 as described above may be,for example, a microelectronic unit as discussed above in connectionwith FIG. 1, or a structure incorporating plural microelectronic unitsas discussed with reference to FIG. 10. In a further variant, both maybe provided, and any number of such structures may be used.

Structure 306 and components 308 and 310 are mounted in a common housing301, schematically depicted in broken lines, and are electricallyinterconnected with one another as necessary to form the desiredcircuit. In the exemplary system shown, the system includes a circuitpanel 302 such as a flexible printed circuit board, and the circuitpanel includes numerous conductors 304, of which only one is depicted inFIG. 25, interconnecting the components with one another. However, thisis merely exemplary; any suitable structure for making electricalconnections can be used.

The housing 301 is depicted as a portable housing of the type usable,for example, in a cellular telephone or personal digital assistant, andscreen 310 is exposed at the surface of the housing. Where structure 306includes a light-sensitive element such as an imaging chip, a lens 311or other optical device also may be provided for routing light to thestructure. Again, the simplified system shown in FIG. 25 is merelyexemplary; other systems, including systems commonly regarded as fixedstructures, such as desktop computers, routers and the like can be madeusing the structures discussed above.

The vias and via conductors disclosed herein can be formed by processessuch as those disclosed in greater detail in the co-pending, commonlyassigned U.S. patent application Ser. Nos. 12/842,717, 12/842,651,12/842,612, 12/842,669, 12/842,692, and 12/842,587, filed on Jul. 23,2010, and in published U.S. Patent Application Publication No.2008/0246136, the disclosures of which are incorporated by referenceherein.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

It will be appreciated that the various dependent claims and thefeatures set forth therein can be combined in different ways thanpresented in the initial claims. It will also be appreciated that thefeatures described in connection with individual embodiments may beshared with others of the described embodiments.

The invention claimed is:
 1. A semiconductor assembly, comprising: asemiconductor element having a front surface, a rear surface remote fromthe front surface, and an opening extending from the rear surfacepartially through the thickness of the semiconductor element, thesemiconductor element further including a plurality of conductive padsat the front surface, and a hole extending through the conductive padsand partially through the thickness of the semiconductor element, thehole meeting the opening at a location between the front and rearsurfaces, wherein at the location where the hole and the opening meet,interior surfaces of the hole and the opening extend at different anglesrelative to the rear surface such that there is a step change betweenslopes of the interior surfaces of the hole and the opening; acontinuous dielectric layer partially overlying the respectiveconductive pads at a location above the respective conductive pads andoverlying an interior surface of the semiconductor material within thehole and the opening; a conductive element electrically contacting theconductive pads, the conductive element having a first portion exposedat the rear surface for electrical connection with an external device,the conductive element having a second portion overlying the continuousdielectric layer; wherein the first portion of the conductive elementhaving a first internal space filled with a dielectric region within theopening and the second portion of the conductive element having a secondinternal space within the hole; and an outer surface of the dielectricregion is located above but parallel to a plane defined by the rearsurface and located below a plane defined a contact surface of the firstportion of the conductive element exposed at the rear surface.
 2. Asemiconductor assembly as claimed in claim 1, wherein the conductivepads have an outwardly facing surface facing away from the semiconductorelement, wherein at least a portion of the dielectric layer contacts theoutwardly-facing surface.
 3. A semiconductor assembly as claimed inclaim 1, wherein the conductive element includes a conductiveinterconnect coupled to the conductive pad and a conductive contactcoupled to the conductive interconnect, the conductive contact beingexposed at the rear surface.
 4. A semiconductor assembly as claimed inclaim 3, wherein the opening has a first width in a lateral directionalong the rear surface, and the conductive contact has a second width inthe lateral direction, the first width being greater than the secondwidth.
 5. A semiconductor assembly as claimed in claim 1, wherein thesemiconductor element includes a plurality of active semiconductordevices and the plurality of conductive pads are electrically connectedwith at least one of the plurality of active semiconductor devices.
 6. Asemiconductor assembly as claimed in claim 1, wherein the conductivepads have an outwardly facing surface facing away from the semiconductorelement, wherein at least a portion of the at least one conductiveelement overlies the outwardly-facing surface and is electricallyconnected thereto.
 7. A semiconductor assembly as claimed in claim 1,wherein the conductive element includes a conductive interconnectexposed at the rear surface for electrical connection to an externaldevice, the conductive interconnect extending into the opening, and aconductive via, extending within the hole and coupled to the conductiveinterconnect and the conductive pads.
 8. A semiconductor assembly asclaimed in claim 7, wherein the conductive interconnect overlies aninner surface of the opening, the conductive interconnect conforming toa contour of the opening.
 9. A semiconductor assembly as claimed inclaim 8, wherein the conductive interconnect extends along a portion ofthe inner surface of the opening.